Seamless cold worked steel tubes but also tubes of other metal materials are usually manufactured by the following main process-steps:
Firstly, steel billets are produced by melting of scrap metal, refining in ladle and converter followed by continuous casting into strands which are cut into billets. The billets are then subjected to hot rolling to form round bars from which hollow tubular blanks are formed by piercing the round bars with a mandrel and further hot rolling or hot-extrusion. It is also possible to manufacture the hollow blanks from ingot cast steel. Finally, the hollow tubular blanks, in cold state, are either drawn or subjected to pilger-rolling to tubes of final dimensions.
Common for the final step of drawing or pilger-rolling is that the outer diameter of the hollow blanks is reduced during the working steps. When manufacturing tubes with large diameters, it is therefore necessary to use hollow tubular blanks with very large diameter as starting material. However, the forces needed to reduce the dimensions of hollow blanks increases rapidly with the size of the hollow blank and therefore increases also the size of the manufacturing equipment, i.e. draw-benches and rolling mills for both hot and cold rolling correspondingly. This results eventually in high production costs.
In the future, the demand for large diameter cold worked seamless steel tubes and the demand for large diameter cold worked seamless tubes of other materials is expected to increase, especially in oil- and gas extraction, and there is therefore a need for more efficient and less costly manufacturing methods for these products.
Consequently, it is an aspect of the present disclosure to provide an effective and cost efficient method of manufacturing tubes. A further aspect of the present disclosure is to provide an effective and cost efficient arrangement for manufacturing tubes.